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NKS Programme Area:NKS-R
Research Area:Severe accidents and Reactor Physics
Report Number:NKS-151
Report Title:Experiments on the behaviour of ruthenium in air ingress accidents
Activity Acronym:Ruthenium Releases
Authors:Teemu Kärkelä, Ulrika Backman, Ari Auvinen, Riitta Zilliacus, Maija Lipponen, Tommi Kekki, Unto Tapper, Jorma Jokiniemi
Abstract:During routine nuclear reactor operation, ruthenium will accumulate in the fuel in relatively high concentrations. In a severe accident in a nuclear power plant it is possible that air gets into contact with the reactor core. In this case ruthenium may oxidise and form volatile ruthenium species, RuO3 and RuO4, which can be transported into the containment. In order to estimate the amount of gaseous ruthenium species, it is of interest to know, how they are formed and how they behave. In our experiments the formation and transport of volatile ruthenium oxides was studied by exposing RuO2 powder to diverse oxidising atmospheres at a relatively high temperature. Transport of gaseous RuO4 was further investigated by injecting it into the facility in similar conditions. Upon cooling of the gas flow RuO2 aerosol particles were formed in the system. They were removed from the gas stream with plane filters. Gaseous ruthenium species were trapped in 1M NaOH-water solution, which is capable of trapping RuO4 totally. Ruthenium in the solution was filtered for analysis. The determination of ruthenium both in aerosol and in liquid filters was made using instrumental neutron activation analysis (INAA). In order to close the mass balance and to achieve better time resolution seven experiment were carried out using radioactive tracer. In this report, the facility for the ruthenium behaviour study and results from experiments are presented. Preliminary conclusions from the experiments are reported as well. Final conclusions will be made after modelling of the facility is completed in a continuation work of this study.
Keywords:Ruthenium; nuclear safety; fission product; aerosol sampling and transport
Publication date:01 Mar 2007
ISBN:ISBN: 978-87-7893-214-3
Number of downloads:921
Download:pdf NKS-151.pdf
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